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From: Theodore Ts'o <tytso@mit.edu>
To: Fengguang Wu <fengguang.wu@gmail.com>
Cc: linux RAID <linux-raid@vger.kernel.org>,
	NeilBrown <neilb@suse.de>, Li Shaohua <shli@fusionio.com>,
	Marti Raudsepp <marti@juffo.org>,
	Kernel hackers <linux-kernel@vger.kernel.org>,
	ext4 hackers <linux-ext4@vger.kernel.org>,
	maze@google.com, "Shi, Alex" <alex.shi@intel.com>,
	linux-fsdevel@vger.kernel.org
Subject: Re: ext4 write performance regression in 3.6-rc1 on RAID0/5
Date: Fri, 17 Aug 2012 11:37:35 -0400	[thread overview]
Message-ID: <20120817153735.GB31297@thunk.org> (raw)
In-Reply-To: <20120817151318.GA2341@localhost>

On Fri, Aug 17, 2012 at 11:13:18PM +0800, Fengguang Wu wrote:
> 
> Obviously the major regressions happen to the 100dd over raid cases.
> Some 10dd cases are also impacted.
> 
> The attached graphs show that everything becomes more fluctuated in
> 3.6.0-rc1 for the lkp-nex04/RAID0-12HDD-thresh=8G/ext4-100dd-1 case.

Hmm... I'm not seeing any differences in the block allocation code, or
in ext4's buffered writeback code paths, which would be the most
likely cause of such problems.  Maybe a quick eyeball of the blktrace
to see if we're doing something pathalogically stupid?

You could also try running a filefrag -v on a few of the dd files to
see if there's any significant difference, although as I said, there
doesn't look like there was any significant changes in the block
allocation code between v3.5 and v3.6-rc1 --- although I suppose
changes in timeing could have have caused the block allocation
decisions to be different, so it's worth checking that out.

Thanks, regards,

						- Ted

  parent reply	other threads:[~2012-08-17 15:37 UTC|newest]

Thread overview: 43+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-08-15 18:33 NULL pointer dereference in ext4_ext_remove_space on 3.5.1 Marti Raudsepp
2012-08-16  2:46 ` Theodore Ts'o
2012-08-16 11:10   ` Fengguang Wu
2012-08-16 15:25     ` Theodore Ts'o
2012-08-16 20:21       ` Maciej Żenczykowski
2012-08-16 20:21         ` Maciej Żenczykowski
2012-08-16 21:19         ` Theodore Ts'o
2012-08-16 21:19           ` Theodore Ts'o
2012-08-16 21:40           ` Maciej Żenczykowski
2012-08-16 22:26             ` Theodore Ts'o
2012-08-16 22:44               ` Maciej Żenczykowski
2012-08-17  6:01       ` Fengguang Wu
2012-08-17 13:15         ` Theodore Ts'o
2012-08-17 13:22           ` Fengguang Wu
2012-08-17 13:50           ` [PATCH] ext4: fix kernel BUG on large-scale rm -rf commands Theodore Ts'o
2012-08-17 17:48           ` NULL pointer dereference in ext4_ext_remove_space on 3.5.1 Christoph Hellwig
2012-08-17 20:34             ` Theodore Ts'o
2012-08-17 20:34               ` Theodore Ts'o
2012-08-17 21:05               ` Christoph Hellwig
2012-08-17 21:05                 ` Christoph Hellwig
2012-08-17 22:55                 ` Dave Chinner
2012-08-17 22:55                   ` Dave Chinner
2012-08-17 23:11                   ` Theodore Ts'o
2012-08-17 23:11                     ` Theodore Ts'o
2012-08-17  6:09       ` ext4 write performance regression in 3.6-rc1 Fengguang Wu
2012-08-17 13:40         ` Theodore Ts'o
2012-08-17 14:13           ` Fengguang Wu
2012-08-17 14:25           ` ext4 write performance regression in 3.6-rc1 on RAID0/5 Fengguang Wu
     [not found]             ` <20120817151318.GA2341@localhost>
2012-08-17 15:37               ` Theodore Ts'o [this message]
2012-08-17 20:44             ` NeilBrown
2012-08-21  9:42               ` Fengguang Wu
2012-08-21 12:07                 ` Fengguang Wu
     [not found]             ` <20120822035702.GF2570@yliu-dev.sh.intel.com>
2012-08-22  4:07               ` Shaohua Li
2012-08-22  5:39                 ` Yuanhan Liu
2012-08-22  6:00               ` NeilBrown
2012-08-22  6:31                 ` Yuanhan Liu
2012-08-22  7:14                 ` Andreas Dilger
2012-08-22 20:47                 ` Dan Williams
2012-08-22 21:59                   ` NeilBrown
2012-09-17 12:21   ` NULL pointer dereference in ext4_ext_remove_space on 3.5.1 Dmitry Monakhov
2012-09-17 13:52     ` Theodore Ts'o
2012-09-17 14:48       ` Dmitry Monakhov
2012-08-16  9:00 ` Fengguang Wu

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